1. Technical Field
The present invention relates to the field of microminiature resonant structures, especially to ribbon, wire, beam, hollow-beam and cantilevered hollow-beam, and double beam resonant structures, and more particularly to the combination of such structures with piezoelectric drive/detection methods and means, and fabrication techniques for making such miniature and microminiature resonant structures. The piezoelectric material is deposited as a thin film, and may be excited electrically or optically.
2. Background Art
Recent developments in microfabrication techniques including micromachining applicable to discrete semiconductors and to integrated circuits (IC's), have brought vast changes to the electronics industries, and have focused attention on smaller, more efficient devices capable of large-scale production at low cost.
Microfabrication and micromachining include the techniques of planar technology, wet chemical etching and other etching techniques, metallization, and metal deposition. Planar technology includes the various techniques used in integrated circuit fabrication, such as photolithography, oxide etching, thermal diffusion, ion implantation, chemical vapor deposition, and dry plasma etching.
Recognition of the need to develop microsensors having photo-optic fiber and microcomponent communications and control techniques in the process control industries has created an unfulfilled need for development of compatible new devices in these industries.
For the purposes of this limited description, "process control" includes both individual variable processes and complex multivariable processes involving a large number of controlled process conditions (or "measurands"), such as fluid flow, flow rate, temperature, pressure, level, and the like. "Station" generally refers to a place, site, base, installation, point, or locality. "Resonant structure" herein generally refers to ribbon, wire, beam, hollow-beam, cantilevered beam and cantilevered hollow-beam, and double beam articles of manufacture, and their equivalent, which can be resonated at particular oscillation frequencies. As used herein, "laminar" refers to morphology characterized by one or more relatively thin layers, as compared with the length and/or width of an object or element. In describing the process steps, the device being fabricated may be referred to as a "workpiece".
Industrial process control apparatus and techniques have evolved over a number of years from relatively simply individual variable pneumatic controllers for separate respective process conditions, to very large integrated systems including sophisticated analog and digital processing equipment with sophisticated communications (telemetering) techniques for remotely communicating the multiple process control signals to and from the site of the process control actuator, which is often a valve, switch, clutch, brake, solenoid, relay, motor or servomotor, or sensor.
The communications/telemetry process may involve (individually or in combination) pneumatic, electric, optical fiber light path, or various other communications media techniques. Converting the communications data to energy to effect change in the process control variable often involves interfacing various energy and communications techniques. Historically, such systems were large and unwieldy and often used substantial amounts of energy.
Techniques for fabrication of certain resonant elements similar to the present invention are disclosed in P. W. Barth, "Silicon Sensors Meet Integrated Circuits", CHEMTECH, November, 1982, pp. 666-673.
Other publications of interest concerning the fabrication techniques used by the present invention include: "Cadmium Sulphide and Zinc Oxide Thin Film Transducers", by N. F. Foster et al, IEEE Transactions on Sonics "Reactive Magnetron Sputtering of ZnO", by B. T. Khuri-Yakub et al, J. Appl. Phys. 52 (7), July 1981, pp. 4772-4774; "Zinc Oxide Film Transducers", by N. F. Foster et al, Applied Physics Letters, Vol. 8, No. 9, 1 May 66, pp. 221-223; "Preparation of ZnO Thin Films by Sputtering of the Compound in Oxygen and Argon", by G. A. Rozgony et al, Applied Physics Letters, Vol. 8, No. 9, 1 May 66, pp. 220-221; "Monolothic Integrated Zinc-Oxide on Silicon Pyroelectric Anemometer", by D. L. Polla et al, IEEE IEDM 83, CH 1973-7/83/000-0639, pp. 639-642; "Thin Zinc-Oxide Film Array for Programmable Filter and Scanned Receiving Transducer", C. T. Chung et al, IEEE 1979 Ultrasonics Symposium, IEEE CH1482-9/79/0000-0915, pp. 915-920; "Heat and Strain-Sensitive Thin-Film Transducers", R. S. Muller, Sensors and Actuators, 4 (Elsevier Sequoia, The Netherlands, 1983), pp. 173-182; "Piezoelectricity in Thin Film Materials," N. F. Foster, J. Acoust. Soc. Am. 70 (6), December 1981, pp. 1609-1614; " Thin-Film Integrated Sensors Respond Down to 0.1 Hz", pp. 15, 17; "The Piezoelectric Crystal as an Air Pollution Monitor", G. G. Guilbault, Plenary Lecture, pp. 637-643; and "Structure and Properties of Vacuum-Deposited Thin Films: A New Basic Relationship", P. S. Vincent et al, Journal of Applied Physics, Vol. 48, No. 9, September 1977, pp. 3800-3806.